Low-static carpet

ABSTRACT

A very fine strand of thinly insulated electrically conductive wire is introduced into a strand of nonconductive yarn composed of natural and/or synthetic fibers to form a conductive composite strand. Such conductive strands of yarn are then woven or tufted with conventional nonconductive strands into a carpet, thereby substantially reducing static electricity effects and, at the same time, protecting persons on the carpet from the danger of severe shock due to a household voltage source being exposed to the carpet.

I United States Patent McCune Feb. 1, 1972 [54] LOW-STATIC CARPET OTHER PUBLICATIONS [72] Inventor: Thomas B. McCuue, Mahopac, NY. Barry, Textile Applications of Metal Fibers, Modern Textiles [73] Assignee: Hudson Wire Company, Ossining, N.Y. Magazme' June 1967 pages 53- 56 [22] Filed: June 10, 1970 Primary ExaminerL. T. l-lix AttorneyDarby & Darby [211 App]. No.: 44,911

[57] ABSTRACT [52] U.S.CI. ..317/2 C, l39/425, 57/157 AS A very fine strand of thinly insulated electrically conductive [51] Int. Cl ..A0ld 43/00, H05f 3/00 wire is introduced into a strand of nonconductive yarn com- [58] Field of Search ..3l7/2 R; 139/425; 57/157 AS posed of natura and/0r synthetic fibers to form a conductive composite strand. Such conductive strands of yarn are then 55 m- Cited woven or tufted with conventional nonconductive strands into a carpet, thereby substantially reducing static electricity ef- UNITED STATES PATENTS fects and, at the same time, protecting persons on the carpet 1,954,855 4/1934 Weaver ..139/425 R from the danger of Severe due to a househcld vo'mge Blumfield Valko ....l39/425 R ....139/425 R source being exposed to the carpet.

12 Claims, 7 Drawing Figures slsasleo'r PATENTED FEB I I972 SHEEI 1 BF 2 FIG. 3

INVENTOR. THOMAS B. McCUNE ATTORNEYS PATENTEDFEB H972 3.639.807

SHEET 2 [1F 2 INVENTOR.

ATTORNEYS THOMAS H MCCUNE LOW-STATIC CARPET This invention relates to the use of very fine thinly insulated wire strands in the construction of carpets.

The carpet industry has long been aware of the problem of static electricity generation, accumulation and discharge which is characteristic of carpet. The generation and buildup of a static electricity charge generally results from the friction produced by a person walking across the surface of a carpet. Static electricity charges varying in intensity up to several thousand volts can build up on the carpet. The amount of charge and its effect depends on the type of material of which the carpet is constructed, the body chemistry of the person walking on the carpet, the material from which the persons shoes are constructed, the prevailing atmospheric conditions, and. possibly other conditions. It can and frequently does cause personal discomfort at the time of static discharge. Furthermore, the buildup of static charges in the person walking across the carpet may create a nuisance in that it can cause clothing to cling to the body.

In the past, efforts toward solving this static buildup problem have involved providing carpets with a fully conductive gridwork of metallic filaments and fibers. However, this interlocking conductive gridwork created a potential danger of severe shock to persons standing on the rug if a source of electric power contacted the carpet. Another attempt solution to the problem was to apply a nonmetallic, antistatic coating to the surface of each strand of yarn by spraying or the like. However, these coatings operated well only within a limited range of atmospheric conditions and had the further disadvantage of being easily removed by substances used to clean the carpet, or by friction due to movement across the surface of the carpet.

The static electricity problem is reduced in accordance with this invention by including in the construction of a rug or carpet a strand of thinly insulated wire. The insulated wire can be either twisted around, laid in parallel to the strand of yarn used in constructing a carpet or laid in perpendicular to the strand of yarn used in constructing the carpet.

It is therefore an object of this invention to produce a carpet construction having a reduced tendency to accumulate a static electricity charge.

It is a further object of this invention to produce a carpet construction which prevents an electrical charge due to a household voltage source exposed to the carpet from being conducted to a person standing on the carpet.

Another object of this invention is to produce a carpet of the type referred to which embodies all of the desirable decorative features ordinarily found in such goods.

Still another object is to produce a carpet of the type referred to which can be easily manufactured and easily cleaned.

These and other objects and features of this invention will be more readily understood and appreciated by reference to the following descriptions and drawings of which:

FIG. 1 is an enlarged perspective view of a strand of yarn embodying the preferred form of this invention;

FIG. 2 is a perspective view of a carpet embodying the preferred form of this invention;

FIG. 3 is a cross-sectional view of an insulated conductive element;

FIG. 4 is a perspective view of a carpet embodying an alternate form of this invention;

FIG. 5 is an enlarged view of the construction of the carpet material illustrated in FIG. 4;

FIG. 6 is a perspective view of a carpet embodying another alternate form of this invention; and

FIG. 7 is an enlarged view of the construction of the carpet material illustrated in FIG. 6.

The low-static carpet of the preferred form of this invention consists of a fiber system having a minor amount of conductive strands and a major amount of nonconductive strands. A nonconductive strand consists of a plurality of electrically nonconductive natural and/or synthetic fibers twisted together in a manner well known in the art to form a strand of yarn. A

conductive strand consists of the nonconductive strand just described with a thinly insulated conductive element either twisted around or laid in parallel to the nonconductive strand.

FIG. I illustrates the construction of a conductive strand ll, wherein an insulated conductive element 12 is twisted into a previously nonconductive strand 13. Whether the insulated conductive element is twisted, or laid in parallel without twisting, around the nonconductive strand depends somewhat on the composition of the strand. If the strand is composed of continuous filament, the insulated conductive element need not be twisted into the strand. However, if the strand is composed of short fibers, it may be preferable to twist insulated conductive element into the strand.

FIG. 3 illustrates in cross section an insulated conductive element 12 partially imbedded in a normally nonconductive strand 13 to form a conductive strand 11. The insulated conductive element 12 consists of an inner metallic core 14 and an outer insulated sheath 15. The diameter of the inner conductor may vary from the largest diameter acceptable for embedding into carpet material from an aesthetic point of view to the smallest diameter having adequate strength for fabricating and wear service. Obviously, thick wires are undesirable since they would be readily seen in the carpet. Likewise, wires that are toofine to be handled in carpet manufacture are unacceptable because they lack sufficient strength to provide adequate service life.

In thepreferred embodiment of this invention, the conductive element consists of a conductive copper core having a 0.004-inch diameter and an insulating sheath surrounding the core composed of oleoresinous enamel and having a wall thickness of 0.0002 inch. However, copper alloys, aluminum and aluminum alloys, steel, copper clad steel and other metallic conductors are suitable for use in the conductive core of this invention. Similarly, the insulating sheath material is not limited to that used in the preferred embodiment. Other suitable insulating materials include polyesters, polyurethanes, polyamides and epoxy compounds. Certain synthetic compounds, such as polyamides, are particularly advantageously employed as insulating materials since they may be dyed to match the color of the nonconductive yarn strands. An oleoresinous insulating sheath similar to that surrounding the metallic conductor in the preferred embodiment is formed by drawing the wire through an oleoresinous solution and then through an oven several times to obtain the desired thickness of insulation. The insulated wire is then ready to be introduced into a nonconductive strand to form the conductive strand of this invention.

The thin insulation sheath surrounding the inner conductive core provides an advantageous safety feature in that it has sufficient dielectric strength to withstand normal household voltage (lO5-l25 v. AC). Accordingly, the danger of severe shock to a person standing on the carpet due to a source of household voltage contacting the carpet is eliminated. This hazard existed in one of the conventional approaches to reducing static electricity in carpets in which a gridwork of metallic elements was interlaced with the nonconductive yarn strands. If a source of household voltage was exposed to this earlier style carpet, the metallic gridwork could conduct current throughout the gridwork and thereby cause a severe shock to a person standing on the carpet although the person was distant from the exposed voltage source. This problem is eliminated by the carpet of this invention due to the thin insulating sheath.

However, since static electricity charges characteristically are of a higher voltage than normal household voltage, they can overcome the dielectric strength of the insulating sheath and penetrate through to the conductive core. Thus, the static electricity charge is either dissipated before being built up or drained off after buildup by the conductive core with no physical or mechanical deterioration or permanent electrical failure to the core. If no insulation were provided for the conductive element of this invention, the dangers inherent in the conventional metallic gridwork carpets would be present. If

too much insulation were provided for the conductive element of this invention, the static electricity voltages would be less than the dielectric strength of the insulation and the static charge would be prevented from penetrating through to the conductive element and being dissipated or drained off. The thinly insulated conductive element of this invention avoids both of the deleterious effects of having no insulation and having too much insulation.

The nonconductive yarn used to make the conductive strand will usually be of the same fiber as the nonconductive strands forming the bulk of the carpet construction. Any of the popular synthetic or natural fibers used in the manufacture of carpet are suitable for use in this invention, e.g., nylon, polyester, wool, cotton, etc. In the actual construction of the conductive element, it is recommended that the nonconductive yarn first be dyed to the desired color causing it to shrink to its final size. The insulated wire is then introduced in the yarn. Introduction of the conductive element into the loosely twisted yarn does not add to the overall diameter, and adds approximately 0.064l gram per linear yard of yarn strand (based on 0.004-inch diameter wire). In a preferred embodiment, the nonconductive fibers are composed of nylon, with the diameter of each fiber being approximately 0.002 inch.

After the thinly insulated conductive element is introduced into the nonconductive strand, the resulting conductive strand is ready to be used in the construction of carpets by conventional weaving or tufting processes. Wires may also be introduced at the weaving operation without having any prior combination with yarn.

FIG. 2 illustrates an enlarged perspective view of a section of carpet constructed in accordance with the preferred embodiment of this invention. Construction of the carpet is based on a system of conductive strands ll, alternating in regular frequency with the nonconductive yarn strands 13 forming the bulk of the system. As will be noted from FIG. 2, every fifth strand in the carpet construction is a conductive strand. However, the number of conductive strands which provides the best effect in a given carpet construction will vary depending on several factors. The material used in constructing the carpet, the composition of the carpet, the dimensions of the nonconductive strand into which the wire is introduced, and the degree of static electricity which is tolerable for a given situation are factors governing the optimum number of conductive strands in a system.

As illustrated in FIG. 2, the conductive strands in the preferred embodiment of this invention are arranged parallel to each other in a spaced relationship in the carpet with the nonconductive strands 13 being intermediate and aligned parallel to the spaced conductive strands.

Referring now to FIG. 4, the thinly insulated conductive elements l2 and 12' may be arranged in a grid network with insulated conductive elements 12 laid in parallel to the rows of conductive and nonconductive strands and insulated conductive elements 12 laid in perpendicular to the conductive and nonconductive strands. Referring to FIG. 5, each of the insulated conductive elements 12 is also laid in parallel in each conductive strand 11 rather than being twisted into the strands as in the preferred embodiment. It is understood that in this alternate embodiment, the conducting strands 11' are designated as conducting because they abut the insulated conductive elements 12 rather than being integral with them.

In a further alternate embodiment of this invention, illustrated in FIG. 6 and FIG. 7, the insulated conductive elements 12" which are laid perpendicular to the rows of nonconductive yarn strands 13 are the only insulated conductive elements in the carpet. In this embodiment, there are no conductive yarn strands" as that term is used above.

It will be obvious to those skilled in the art that the insulated conductive elements may also be nonparallely aligned or may be aligned in abutting relationship to one another. No danger is presented by having the thinly insulated wires cross over and/or touch each other. As previously mentioned, the dielectric strength of the insulating sheath is adequate to prevent penetration to the conductive core by ordinary household voltages. Furthermore, the dissipation of the static electricity charge is not hampered by having the thinly insulated conductive elements cross over and/or touch each other. Nor does it matter whether the conducting strands lie in the warp or the woof of the carpet.

It has been reported that static electricity levels as high as 35,000 volts have been generated in a carpet. In the carpet of the preferred embodiment of this invention in which every fifth strand is a conductive strand, electrostatic voltages have been reduced to 3,500 volts or less, thereby eliminating, for most people, the discomfort of being shocked.

While certain embodiments of the invention have been shown in the drawings, it is to be understood that this disclosure is for the purpose of illustration only and that various changes in shape, proportion and arrangement of parts, as well as the substitution of equivalent elements for those herein shown and described, may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

l. A low-static carpet comprising a plurality of nonconducting strands forming the carpet and a plurality of metallic conductors in the carpet, each of said metallic conductors having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet.

2. The low-static carpet defined in claim 1 further comprising a plurality of conducting strands, said conducting strands including said conductor having said sheath.

3. The low-static carpet defined in claim 1, wherein said metallic conductor consists of a copper wire and said insulating sheath consists of oleoresinous material.

4. A low-static carpet comprising a plurality of nonconducting strands, forming the carpet and a plurality of metallic conductors in the carpet, each of said metallic conductors having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet, said insulating sheath being a material selected from the group consisting of polyesters, polyurethanes, polyamides and epoxy compounds.

5. The low-static carpet defined in claim 2, wherein said nonconducting strands comprise a majority of the carpet and said conducting strands comprise a minority of the carpet and said conducting strands are parallely aligned in spaced relationship to each other.

6. The low-static carpet defined in claim 5, wherein a plurality of said nonconductin g strands are aligned parallel to one another and intermediate said conducting strands.

7. The low-static carpet material defined in claim 5, wherein said nonconducting strands extend perpendicular to said conducting strands.

8. A low-static carpet comprising a plurality of nonconducting strands and a plurality of conducting strands, each of said conducting strands including a metallic conductor having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet, said conductive and nonconductive strands consisting essentially of yarn.

9. A low-static carpet comprising a plurality of nonconducting strands, forming the carpet and a plurality of metallic conductors in the carpet, each of said metallic conductors having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet, each of said sheathed conductors being aligned perpendicular to said nonconducting strands.

10. A low-static carpet comprising a plurality of nonconducting yarn strands and a plurality of conducting yarn strands, said conducting strands including a metallic conductor and an electrically insulating sheath on said metallic conductor having a dielectric strength greater than that required to insulate against normal household voltages contacting said conducting yarn strands.

11. The low-static carpet recited in claim 1 wherein the number and arrangement of said metallic conductors is sufficient to substantially reduce the normal static charges generated in the carpet by a human treading on the carpet.

12. A low-static carpet comprising a plurality of nonconducting yarn strands and a plurality of conducting yarn strands, each of said conducting strands including a metallic conductor, the number and arrangement of said metallic conductors being sufficient to substantially reduce the normal static charges generated in the carpet by a human treading on the carpet, each said metallic conductor having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against ,normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet. 

1. A low-static carpet comprising a plurality of nonconducting strands forming the carpet and a plurality of metallic conductors in the carpet, each of said metallic conductors having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet.
 2. The low-static carpet defined in claim 1 further comprising a plurality of conducting strands, said conducting strands including said conductor having said sheath.
 3. The low-static carpet defined in claim 1, wherein said metallic conductor consists of a copper wire and said insulating sheath consists of oleoresinous material.
 4. A low-static carpet comprising a plurality of nonconducting strands, forming the carpet and a plurality of metallic conductors in the carpet, each of said metallic conductors having an electrically insulating sheath, each said sheatH having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet, said insulating sheath being a material selected from the group consisting of polyesters, polyurethanes, polyamides and epoxy compounds.
 5. The low-static carpet defined in claim 2, wherein said nonconducting strands comprise a majority of the carpet and said conducting strands comprise a minority of the carpet and said conducting strands are parallely aligned in spaced relationship to each other.
 6. The low-static carpet defined in claim 5, wherein a plurality of said nonconducting strands are aligned parallel to one another and intermediate said conducting strands.
 7. The low-static carpet material defined in claim 5, wherein said nonconducting strands extend perpendicular to said conducting strands.
 8. A low-static carpet comprising a plurality of nonconducting strands and a plurality of conducting strands, each of said conducting strands including a metallic conductor having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet, said conductive and nonconductive strands consisting essentially of yarn.
 9. A low-static carpet comprising a plurality of nonconducting strands, forming the carpet and a plurality of metallic conductors in the carpet, each of said metallic conductors having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet, each of said sheathed conductors being aligned perpendicular to said nonconducting strands.
 10. A low-static carpet comprising a plurality of nonconducting yarn strands and a plurality of conducting yarn strands, said conducting strands including a metallic conductor and an electrically insulating sheath on said metallic conductor having a dielectric strength greater than that required to insulate against normal household voltages contacting said conducting yarn strands.
 11. The low-static carpet recited in claim 1 wherein the number and arrangement of said metallic conductors is sufficient to substantially reduce the normal static charges generated in the carpet by a human treading on the carpet.
 12. A low-static carpet comprising a plurality of nonconducting yarn strands and a plurality of conducting yarn strands, each of said conducting strands including a metallic conductor, the number and arrangement of said metallic conductors being sufficient to substantially reduce the normal static charges generated in the carpet by a human treading on the carpet, each said metallic conductor having an electrically insulating sheath, each said sheath having a dielectric strength greater than that required to insulate against normal household voltages and less than that required to insulate against normal static charges generated in the carpet by a human treading on the carpet. 